Rather than cutting out the story, simply abberviate it.

Cut out all the fetch quests and move the minor story points to side-stories, but keep the main thrust of it. Enough that you cut down the 50->60 quests to a good manageable chain of 15-20, with say 30-40 or so for total 3.X content. This gives you about 45-60 quests between level 50 and the new expansion without getting anyone lost.


For example almost all of the post-50 primal stuff (levithan, king mog, etc..) could be side quests without losing out on what you need to keep players up to date for on the main story (crystal braves, ul'dah).